Ignition system



April 16, 1940.

H. RABE'IzzANA 'Er AL IGNITION SYSTEM Filed Feb. 27. 1959 s spgm-snee; 2

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April 16, ,1940. H, RABEzzANA ET AL' IGNITION SYSTEM Filed Feb. 27, 19595 Sheets-Sheet 5 uRRENT m UPPER HALF OF lfl v Patented Apr. 16, 1940UNITI-:D si'ii'rlzsv PATENT oi-*HCE IGNITION SYSTEM corporation ofFlint, and Wilfred A. chinsky. Ann Arbor, Mich., assignnrs to GeneralMotors Corporation, Detroit, Mich.,

Delaware Applicaties resi-nn zu. 193s, semi No. zsasse rz claim. (ci.12s-14s) 'I'his invention is an improvement on the ignition Systemdescribed and claimed in Patent No. 2,047,431 granted to Donald W.Randolph on July 14, 1936. In that application there is dis- .s closedan impulse operated system especially adapted for use 'as an ignitionsystem for automobiles in which a plurality of impulse producingcircuits, each preferably consisting of a source of energy, aninductance and an-interrupter iiil ii) series, are timed to alternatelydischarge into a common circuit containing a device, lpreferably atwoelectrode electrical valve, adapted to break downen application ofsumcient voltage so as to permit passage of a surge of current. Thisiiow L of current is preferably utilized to produces. high voltagedischarge/"in a circuitY containing an ignition device. This isaccomplished by cou` pling the tube circuit with the ignition circuit bymeans of a step-up transformer. To increase the instantaneous energy ofthe discharge and at the same time obtain a high frequency impulse acondenser is provided across each of the irn-` pulse producing circuits.the condensers' being arranged in series with Aeach other and with theelectrical valve. x

According to one feature of the present invention Randolphs circuit iss'impliiled by eliminati ing one of the condensers. and so arranging theother as to alternately store the energy of the impulses from theVdischarge circuits. This is accomplished by simply connecting acondenser of suiilcient capacity across the inductances 4and a separatecondenser, tube and transformer is.,-

provided for-each of the spark plugs and a dis-v tributor isprovided,preferably betweenthe impulse producingcircuits and the condensers, todistribute the charges to them in proper sequence.

-An advantage of this arrangement is that the d transformers maybemounted on the plugs and the ,length of the secondary leads may bereduced to a'minimum. In present day ignition systems long secondaryleads are employed. These must be well shielded to prevent interferencewith rado transmission and reception and because of their length,together with shielding, their capacity is very considerable and affordsa path for leakage of a considerable amount of the energy of the system.At the same time the high 55 tension leads are subject to rapiddeterioration in service. With secondaryleads of minimum Omer objectsand advantagesof the invention will be pointed out in the course of the'following ll description taken in connection with theaccompanyinsdnwlnsainyvhieh:

Figure 1 is a diagrammatic view showing one form of the improvedcircuit.

Figure 2 is a graph showing the variation of 20. current with time inthe operation of the ignition system of Figure 1.

Figure 3 is a diagrammatic view showing the preferred form of improvedcircuit as applied a three cylinder engine.

. 2s Figure'4 is a longitudinal section through one form oftube-transformer unit mounted on a sparky plug.

Figure 5 isa side'elevation of a similar but slightly modifiedtube-transformer unit. 30

Figure isa section online 5-6 of Figure 5. Figure? is a sectionon line1-1 of Figure 6..` l Figure 8 is a atic. view showing a modined form ofcircuit.

Figure!! is a graph showing the current-time relations in the operationofthe circuit of .Figure 8. v

The ignition circuit shown in Figure 1 is designed for use with afour.cyiinderinternal combustion engine but maybe readily adapted by thoseskilled in the art for servicewith engines having any number ofcylinders.-

Li and le indicate inductances, having magnetizable cores. fedwithcurrent from a common` connection to a suitable battery B or othersource of 5 electrical energy. In series with inductance Li is` theinterrupter I1, and in series with the rinductance La is interrupter Iz.The interrupters `are preferablyoperated by a common engine-l driven camil preferably provided with two o lobes as shown and operated atone-half engine lspeed.

are connected to discharge 'into a condenser C in series with electricalvalve V and the primary P of a step-up transformer. 'I'he condenser C isconnected across the interrupters 11h as shown.

The valve Vis preferably of the type disclosed in the prior Duiendackand Wolfe Patent No. 2,122,932, granted July 5, 193,8, and consists oftwo electrodes, one or both ofwhich are preferably made of a durablealloy containing low work function material, preferably barium in anickelcopper-barium alloy, `the `electrodes being surrounded by anatmosphere of inert gas at sumcient pressure tosupport'arc discharge.Since the voltage available is low the valve must have a relatively lowbreak-down voltage and, at the same time be durable and capable ofresisting arcing over long periods of time.

The secondary S of the step-up transformer is connected in series withthe distributor D arranged to direct current to the spark plugs I2 insuccession in well known manner. Transformer P-S is preferably providedwith an iron core which may consist of thin sheets of iron or ofparticles of iron powder suitably insulated from eiach other to reducelosses due to eddy currents, e c.

Operation-With the parts in the position shown in Figure 1 with theinterrupters closed, battery B stores energy in the inductances L1 andLe. This condition is indicated in the graph, Figure 2, by theincreasing ordinates of the curves at the left of the graph. Thischarging is continued until the interrupter I1 suddenly opens, causingthe inductance L1 to discharge into the condenser C through a pathincluding battery B and closed interrupter In'. The suddenness of thecollapse of the magnetic fieldof the inductance results in thedevelopment of a considerable voltage in the circuit. When the voltageacross the terminals of the condenser C reaches the break down voltageof the valve V, the valve breaks down and a high frequency surge ofcurrent takes place in the tube circuit. 'Ihis surge is converted by thetransformer P--S into a high voltage, high frequency surge in thesecondary circuit and the distributor is so timed with respect to theinterrupter that this surge takes place when the distributor is inposition to carry the current to one of the spark plugs therebyproducing ignition in one of the cylinders. Following the discharge,interrupter I1 closes. Y

In the meantime the current builds up in the circuit containinginductance L2 as indicated by the dotted line curve in Figure 2 untilinterrupter I2 is suddenly opened, causing discharge of energy from theinductance La to the condenser C through a path including battery B andlclosed interrupter I1, thereby charging the condenser to the oppositepolarity, and upon attaining thev necessary voltage, discharge takesplace from the condenser throughv the valve V and transformer P-S toanother one of the plugs in the same manner as described above.Thereafter interrupter Iz closes, beginning another cycle which is arepetition of that described above.

It will be noted that the condenser C'is rst charged to one polarity andthen to the other. This correspondingly reverses the direction ofdischarge through the valve V preventing the building up of metal on oneelectrode and the pitting of the other, with consequent eventualshort-circuiting of the electrodes as is often the case where thedischarge through the valve is al- 'waysin one direction. The circuitalso possesses the advantage that but one condenser is required in thetube circuit, thus reducing cost.

The preferred form of circuit shown in Figure 3 embodies the sameprinciple as the circuit of Figure 1, but is modiiled to make possiblethe location of the transformer close to the plugs so as to reduce thelength of the secondary leads to a minimum. The circuit of Figure l isfurther modified to require the use of an electric valve for each sparkplug, thus reducing the period o! time during which each valve is inoperation and so greatly increasing valve life. The provision ofindependent valves makes it necessary to employ a separate condenser foreach valve.

Another improvement consists in the use' o ballast resistances to holdthe current in the impulse producing circuits within desirable limits.The circuit of Figure 3 is designed to provide ignition for a threecylinder four cyclev engine. This application has been selected tosimplify illustration of the system but obviously the in vention can beapplied to an engine of any nurnber of cylinders.

Referring now to Figure 3, B indicates the battery, Li and Le theinductances, and I1 and Iz the interrupters actuated by cam il which isdriven atone-fourth crankshaft speed and is provided with three lobes asshown.

Between the battery B and the inductances L1 and In is preferablyarranged a tube R containing constant current type ballast resistancesRl and Rz. These resistances each preferably consist of a nlament ofsubstantially pure iron in an atmospherel of hydrogen, but other knowntypes of such resistances may be used. The resistances are designed tomaintain the current passing `through them fairly constant over a widerange of applied voltages and act in the following manner: As thecurrent increases, the resistance of the iron wire increases therebyreducing the flow o! current and tending to return it to its originalvalue. Conversely as the current decreases the resistance of the wiredecreases thereby increasing the iiow of current and tending to enableit to regain its original value.

The use of a ballast resistance insures a sumcient supply ofcurrentunder substantially all operating conditons. It also preventsinjury to the coils in case the ignition is left on with the engine notrunning or in the similar case of very low speed operation.

The ballast resistance also improves high speed performance of thesystem for at such speeds the ingnition voltage tends to fall oii'because of reduction in time during which the inductances receive energyfrom the battery. This reduction is offset by corresponding reduction ineifectiveness of the ballast resistance.

The impulse producing circuits, just described, supply energy tocondensers Ci C: and C: which in turn discharge into independentcircuits each containing in series an electric valve Vi V1 or Vs and theprimary coil Pi Pz or P: of a step-up transformer. The correspondingsecondaries Si Sn and Si supply ignition current to plugs 2|, 22

and 23 respectively.

A distributor D is provided to supply energy to the condensers in propersequence. 'I'his distributor preferably takes the form of circuit makersMi Ma and M: actuated by cam 2l provided with two lobes. as shown anddriven at one-fourth crankshaft speed.

With the construction shown applied to a four cycle engine having threecylinders, it will be apparent that during a complete engine. cycle, u

' shown). to one side of the corresponding conthat k, during tworevolutions of the crankshaft, the circuit breaker cam Il will haverotated 180 and will have elected threesucceasive breaks of the impulseproducing circuits, one circuit being' The parts are so timed'that oneof the circuit.

makers is closed just before and during the time that one o! theinterrupters I1 or I: is being opened thereby clodng the circuit to thecorresponding condenser. This permits the condenser to be charged by thesurge of current, and upon attaining sufiicient voltage, to dischargethrough the corresponding electric valve and through the primary Aof thetransformer, thus producing a spark at the plug.

It will be noted that the arrangement is such that each condenser isfirst charged to one polarity and then to the othenthereby reversing thedirection of discharge through the valves and prolonging their llfe.This is made clear in the folllowing description in which .theconvention is adopted that when the upper plate of the condensers asillustrated on Figure 3 are lgiven, a positive charge the condensers aresaid to have positive polarity and vice versa. It will beunderstooduthat charging of the condenser is in every case followedimmediately by its discharge through the tube circuit to produceignition. To avoid repetition no further mention will be made ofcondenser discharge in the following description. Beginningwith theparts in the position shown in Figure 3 in which both interrupters I1and I: are ,closed and all oi' the circuit makers are-open, and assumingthatthe cams le and Il rotate in the direction indicated by the arrows,circuit maker Mz clos. then interrupter L opens, thereby chargingcondenser C: to positive polarity'. Next-circuit maker Mn closes andinterrupter Ii opens, thereby charging condenser Ci to negativepolarity. Circuit maker Mrnow closes and ,interruptor I'a opens, therebycharging condenser C: tovpodtive polarity. Next circuit maker Mz againcloses, and interrupter I1 opens thereby again charging condenser C: butto negative polarity. Circuit maker M1 Main closes, ,and

interrupterh opens thereby again charging condenser C1 t0 pdtivepolarity. Circuit maker Ms again closes, interrupter I1 opens, therebycharging condenser C: to negative polarity. 'niereafter the cycle isrepeated, charging each co denser alternately to opposite polarities Animportant advantage of the system just described is the fact that camsfor the 'circuit interrupters and circuit makers may be designed togiveanydesired spacing ofthesparks.

. 'me improved ignition system is preferably so constructed-in practicethat the transformer and preferably the electric valve as well aremounted as close to the spark plug as possible. In Figure 4 there isshown a suitable design of valve-transformer assembly.V Here 2iindicates a conventional type of spark plug provided with radioshielding indicated at 2l. To the shield 20 -is secured by a suitablescrew-'threaded coupling III,

a die cast housing 31 containing in one end andenser. The other end ofthe primary is connected by lead l2 to one of the electrodes of electricvalve Il, lthe other electrode being connected to insulated terminal Itwhich is connected by a suitable conductor -(not shown) tothe other sideof thecondenser. indicates a layer of compressible cement, such asasbestos cement, which may be applied to theglass envelope 5l of theelectric valve. The purpose of this is to protect the envelope againstthe heat of die casting should it be found desirable to cast the housing32 about the assembly as shown.

In Figures 5, 6 and 7 there is shown 4a slightly modified form ofvalve-transformer assembly. Here 2l indicates the shielding of the plug.indicates the lower half of a longitudinally split housing for the tubeand transformer. The part 52 is provided with lugs Il and 56 adapted tohave a bayonet or other type of quick detachable connection indicated at51 with the upper end of the plug shield 18. 'Ihe upper portion 58 ofthe housing is held to the lower portion by means of suitable springclips 6I of the typecommonly used Ato hold distributor caps in place.

In the modication shown in'Figure 8 the finductances L1 -and Lz have acommon core as The impulse producing circuits just described dischargealternately as before into condenser C which, upon attaining thenecessary voltage, discharges through^valve V into the primary P1 Pz Psor P4 in' the sequence determined by the distributor D', producing asurge in the corresponding secondary circuit Si Sz Sior S4 and sparkingat the corresponding plug.

In Figure 9 is illustrated the current-timevrelations obtaining with thecircuit of Figure 8 with proper timing oi. the interrupters. Owing tothe employment of a common core for the inductances it is necessarythatbut one of the interrupters be `closed at a time. Otherwise openingci' one of the impulse producing circuits at its interrupter wouldresult in discharge of the energy of the impulse through the closedimpulse producing circuit which, because of the common e0re. 'would a'ctas a short-circuited secondary.

Consequently the time during which energy can be stored in either of theinductances must be somewhat less than the time between sparks. Incommon with the form of circuit shown in Hgure l, the circuit of Figure9 possesses the advantage that but a single main condenser is employed.The distributor D' could, 1r desired, be arranged in the secondarycircuit but the illustrated arrangement has the advantage that thetransformers may be mounted on the spark plugs with the advantagespointed out in Aconnection with the circuit of Figure 3. Our improvedignition system is susceptible of a great deal of modification. It may,of course, be designed for engines of any number of cylinders. It maylikewise be adapted for double ignition systems in which two spark plugsare provided for each cylinder. The usual arrangements for obtainingmanual or automatic spark advance may be applied to the new system. Inthe case of the circuit of Figure 3 it will be found convenient toprovide acommon drive for the interrupter cam I6 and the distributor Dand to provide a common mounting for the interrupters I1 and In and thecircuit makers Mi Mz and Ma so that the spark advance mechanism, whethermanual or automatic, may simultaneously adjust the position oi' theinterrupters and circuit makers with respect to their respective camsfor the circuit makers should always close prior to the opening of theinterrupters to permit eiiicient charging of the correspondingcondensers, 'and reduce sparking at the interrupters. Othermodifications will occur to those skilled in the art.

We claim:

1. The combination of a source of direct current, impulse producingcircuits arranged in parallel and including said source, means fortiming said impulse producingy circuits to cause them to alternatelyproduce electrical impulses, a condenser connected to said circuits` soas to be charged to one polarity by one of said circuits and then to theopposite polarity by the other of said circuits and so on alternately,and a discharge circuit for said condenser vcomprising a device adaptedto normally prevent passage of current therethrough but to break downand permit passage of a surge of current upon application ofpredetermined voltage.

2. In the combination as defined in claim 1, a work circuit coupled tosaid discharge circuit.

3. In the combination as deiined in claim 1, a work circuit including anignition device inductively coupled to said discharge circuit.

4. In an ignition system the combination of a plurality oi impulseproducing circuits, each circuit consisting of van inductance and aninterrupter in series, means for supplying current to said circuits,said interrupters being timed to alternately produce impulses in saidcircuits, a condenser connected to said circuits so as to be chargedfirst to one polarity by one of said circuits and then to oppositepolarity by the other circuit upon actuation of said interrupters, adischarge circuit for said condenser comprising an electric valveadapted to break down upon application of suiiicient voltage in serieswith the primary of a step up transformer, and an ignition device inseries with the secondary of said transformer.

5. In an ignition system the combination of an electrical impulseproducing circuit, a plurality of condensers, means ior connecting veachof said condensers in succession to said circuit to receive a chargetherefrom, and a discharge circuit for each of said condenserscomprising an electrical valve adapted to become conducting uponapplication of suilicient voltage and an ignition device inductivelycoupled to said discharge circuit.

6. In an ignition circuit the combination oi a plurality of electricalimpulse producing circuits, means for alternately producing impulses insaid circuits, a plurality of condensers, means for connecting each ofsaid condensers in succession to each of said circuits, and a dischargecircuit connected to each of said condensers comprising an electricalvalve adapted to become conducting upon application of suiiicientvoltage and an ignition device inductively coupled to said circuit.

'7. In an ignition system the combination of an electricalimpulse'producing circuit comprising an inductance andan interrupter inseries, and means i'or supplying current to 'said circuit, a pluralityof condensers, means for connecting each of said condensers insuccession to said circuit to receive a charge therefrom, and a dls- Ycharge circuit for each of said ondensers comprising an electrical valveadapted to become conducting upon application of sufiicient voltage,

A and an ignition device inductively coupled to said discharge circuit.

8. In an ignition circuit the combination of a plurality of electricalimpulse producing circuits each comprising an inductance and aninterrupter in series, and means for supplying current to said circuits,saidinterrupters being timed tovalternately produce impulses in saidcircuits, a plurality of condensers, means for periodically connectingeach of said condensers in succession to each oi' said circuits toreceive charges therefrom, and a discharge circuit for each of saidcondensers comprising an electrical valve adapted to become conductingupon application of sutilcient voltage, and an ignition deviceinductively coupled to said discharge circuit.

9. In an ignition circuit the combination oi a vplurality of electricalimpulse producing -circuits each comprising an inductance,l aninterrupter and a source oi' current in series, said source being commonto said circuits, said interrupters being timed to alternately produceimpulses in said circuits, a plurality of condensers, means forperiodically connecting each of said condensers across said interrupterswith the interrupters in series with such condenser so that when one ofthe interrupters is opened the condenser in series therewith is chargedto one polarity and with the other interrupter opened the condenser inseries therewith is charged to opposite polarity, and a dischargecircuit for each of said condensers comprising an electrical valveadapted to become conducting upon application of suiiicient voltage, andan ignition device coupled to said discharge circuit.

10. In an ignition circuit the combination ot a plurality of electricalimpulse producing circuits each comprising an inductance, an interrupterand a source of current in series, said source'being common to saidcircuits, said interrupters being timed to alternately produce impulsesin said circuits, a plurality of condensers, means for periodicallyconnecting each of said condensers across said interrupters with theinterrupters in series with such condenser so that when one of theinterrupters is opened the condenser in series therewith is charged toone polarity and with each comprising an inductance', an interrupter, aballast resistance, and a source of current in series, said source beingcommon to said circuits,

said interrupters being timed to alternately produce impulses in saidcircuits, a plurality of condensers, means for periodically connectingeach la plurality of electrical impulse producing circuits of saidcondensers across saidinterrupters with the interrupters in series withsuch condenser so plication of suflicient voltage, and an ignitiondevice coupled to said discharge circuit.

12. In an ignition system the combination of a spark plug and a housingmounted thereon containing a transformer having one side of itssecondary in conducting relation with the insulated electrode of theplug and the other in conducting relation with the spark plug shell, andan electrical valve in said housing having a plurality of spacedelectrodes, one oi said electrodes being connected to one side of theprimary of said transformer, a pair of insulated terminals mounted -onsaid housing, one connected to the other electrode of said valve and theother to the other side of said primary coil.

13. In the combination as dened in claim 12, said housing and shellforming a substantially complete enclosure for said parts preventing thetransmission of radio waves.

14. The combination of a plurality of impulse producing circuitsarranged in parallel, means for timing said impulse producing circuitsto cause them to alternately produce current impulses, a condenserconnected to said circuits so as to be charged to one polarity by one ofsaid circuits and then to the opposite polarity by the other vof saidcircuits and so on alternately, and means in series with said condenseradapted to normally prevent discharge thereof but to break down andpermit discharge when the charges thereon build up to a sumcientvoltage.

15. The combination of a plurality of impulse producing circuitsarranged in parallehmeans for timing said impulse producing circuits tocause them to alternately produce current impulses, a condenserconnected to, said circuits so as to be charged to one polarity by oneof said circuits and then to the opposite polarity by the other vof saidcircuits and so on alternately, and means in series with said condenseradapted to normally prevent discharge thereof but to break down andpermit discharge when the charges thereon build up to a suiilcientvoltage, and a circuit including an ignition device inductively coupledto said last-named circuit.

16. In an ignition system the combination of a ,source of electricalenergy and a plurality o circuits connected to said source in parallel,each circuit comprising an inductance and a circuit breaker in serieswith said source. means for timing said circuit breakers to cause thecircuits to alternately produce current impulses, a condenser inparallel with both of said circuit breakvers and in series with saidinductances so as to be charged first to one polarity by one oi' saidcircuits and then to the opposite polarity by the other of said circuitsand so on alternately, and a discharge circuit for said. condenserincluding an electric valve adapted to break down when the charges onsaid condenser build up to a suicient voltage.

17. In an ignition system the combination of a.

source of electrical energy and a plurality of cirvcuits connected tosaid source in parallel, each,

circuit comprising an inductance and a circuit breaker in series withsaid source, means for timing said circuit breakers to cause thecircuits to alternately produce current impulses, a condenser-inparallel with both of s aid circuit breakers and in series with saidinductances so as to be charged -rst to one polarity by one of saidcircuits and then to the opposite polarity by the other of said circuitsand so on alternately, and a discharge circuit for said condenserincluding an electric valve adapted to break down when the charges onsaid condenser build up to a sutilcient voltage, and a circuit includingan igniting device coupled to said discharge circuit.

s HECTOR. naBEzzANA- wnmnn A. BYcnINsKY.

